1. Building Differentiated Services Using the Assured Forwarding PHB Group Juha Heinänen Telia Finland Inc. jh@telia.fi

2. © Juha Heinanen2 AF PHB Group (RFC 2597) l Provides forwarding of IP packets in four independent service classes ä at each hop, each class has its own, configurable forwarding resources l within each class, an IP packet is assigned one of three levels of drop precedence älower drop precedence means higher probability of forwarding

3. © Juha Heinanen3 AF PHB Group Implementation l forwarding resources (buffer space and bandwidth) can be allocated using ä FBA, CBQ, WFQ, priorities, etc. l dropping of packets is based on the Random Early Drop (RED) algorithm äeach level of drop precedence (green, yellow, red) has its own RED threshold

4. © Juha Heinanen4 Example of Output Behavior R R R R R R R R R R R R Each AF class has its own queue and forwarding resources Each AF class has its own queue and forwarding resources RED threshold for “Red” packets RED threshold for “Yellow” packets

5. © Juha Heinanen5 RED with Multiple Thresholds Discard Probability Average Queue Length 0 1 “Red” Threshold 0 “Yellow” Threshold “Green” Threshold “Red” Packets “Red” Packets “Green” Packets “Green” Packets “Yellow” Packets “Yellow” Packets Full

6. © Juha Heinanen6 AF Based Services l service characteristics of an AF class depend on ätraffic conditioning actions at the edge ärelative traffic load and scheduling policy of the class in the core l different combinations result in relative or quantitative bandwidth and/or delay assurances

7. © Juha Heinanen7 Metering, Marking and Policing Host Enterprise Network Enterprise Network ISP May police host behavior and classify packets on behalf of host May police host behavior and classify packets on behalf of host Polices aggregate behavior and remarks or drops excess Polices aggregate behavior and remarks or drops excess May meter aggregate behavior, classify, (re)mark, drop, and shape packets May meter aggregate behavior, classify, (re)mark, drop, and shape packets May meter host behavior and shape packets May meter host behavior and shape packets R R R May classify packets to service classes May classify packets to service classes May select outgoing packets and drop excess May select outgoing packets and drop excess

8. © Juha Heinanen8 Examples of Markers l Two Rate Three Color Marker (trTCM) ämarks packets green, yellow, or red based on Peak and Committed Information Rates äuseful when peak rate needs to be enforced l Single Rate Three Color Marker (srTCM) ämarks packets green, yellow, or red based on a rate and two burst sizes äuseful when only burst size matters

9. © Juha Heinanen9 New token PIR times/sec New token CIR times/sec ? Not enough yellow tokens Enough yellow tokens, but not enough green tokens Enough yellow and green tokens PBS CBS A Two Rate Marker

10. © Juha Heinanen10 New token CIR times/sec Overflow tokens from C Tc Te ? Not enough green nor yellow tokens Enough yellow tokens, but not enough green tokens Enough green tokens CBS EBS A Single Rate Marker

11. © Juha Heinanen11 Selection of Outgoing Traffic... Link Service Classes Outgoing “streams” Guaranteed Minimum Allowed Maximum Weight Guaranteed Minimum Allowed Maximum Weight Guaranteed Minimum Allowed Maximum Weight Guaranteed Minimum Allowed Maximum Weight

12. © Juha Heinanen12 Assured Bandwidth (AB) Service l traffic is policed at the ingress using one of the two three color markers l green packets are delivered with high probability, yellows as best effort, and reds are discarded l resources are allocated so that the AF class is only moderately loaded with greens

13. © Juha Heinanen13 Assured Delay (AD) Service l traffic is policed so that only green packets are allowed into the network l green packets are delivered with high probability and low delay variation l resources are allocated so that the AF class is very lightly loaded with greens

14. © Juha Heinanen14 VoIP/Web Example IP PBX PSTN VoIP GW ISP 512 Kb AD PRI ISDN 128 Kb AD Web Server 10 Mb AB Enterprise Network Enterprise Network 20 Mb AB 128 Kb AD No Profiles

15. © Juha Heinanen15 Service Implementation R R R R Assured Delay WFQ Weight: 80 % Assured Bandwidth WFQ Weight: 20 % Assured Bandwidth WFQ Weight: 20 % R Policer keeps links only lightly loaded with green packets Best Effort service can implemented as an AB Service with CIR = 0 Best Effort service can implemented as an AB Service with CIR = 0

16. © Juha Heinanen16 Mapping AF PHBs to ATM l each service class is allocated a set of forwarding resources on every link l signaling of UBR VCs is extended by a service class indicator l hierarchical scheduling first per service class and then per VC within the class l AF drop precedence is mapped to the CLP bit

17. © Juha Heinanen17 ATM Backbone Example of Diff-Serv Mapping R R UBR VC for Assured Delay Service UBR VC for Assured Bandwidth Service Drop Prec ATM CLP 0 0 1 1 R R R R

18. © Juha Heinanen18 Summary l AF PHB group provides a flexible means to implement services for both delay sensitive and delay insensitive applications l AF support is already available at least in a limited form in popular routers l AF based services will become available from ISPs during 1999